This invention relates to an injection locked RF oscillator, and to a method of generating RF energy.
It is known that if a signal having a frequency close to the free running or resonance frequency of an oscillator is injected into the oscillator, the oscillator will phase-lock onto the injected signal. The phenomenon is known as injection locking. The same applies where the signal being injected has a harmonic which is close to the resonance frequency of the oscillator. In this event the oscillator will phase-lock onto the harmonic in question.
The resonance frequency of an RF source may be affected by a number of factors. One of these, for example, is temperature. A difficulty hitherto experienced with injection locking of an RF source is that, to increase the lock range--i.e. the range of resonance frequencies over which the system will hold lock once lock has been acquired--the power of the injected signal has to be increased. The injected power required to enable a system to hold lock in most applications was such as to render injection locking impractical as a means of frequency stabilizing an RF source.
It is an object of the invention to provide an injection locked RF oscillator which has a wide lock range without requiring an excessive amount of injected power.